JP3233336B2 - Optical detector for Echelle spectrometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a detector used in an Echelle spectrometer.

[0002]

2. Description of the Related Art Atomic spectroscopy is widely used in atomic emission, atomic absorption, and atomic fluorescence. In particular, a spectrometer of an echelle manifold where the echelle grating is used to disperse the desired radiation,
It has been proved that it has excellent characteristics in terms of resolution and design as compared with a conventional spectrometer using a high ruled line density diffraction grating. In the Echelle spectrometer,
A better resolution of the spectral lines is derived from the fact that the resolution increases with increasing diffraction order. For example, using an order of 20 to 90 provides better resolution than using an order of 1 to 3. Also, the physical size of the spectrometer can be reduced by using an echelle grating.

When using echelle gratings, the various diffraction orders usually lie on top of each other. Usually, prisms are used to separate orders after diffraction by a grating, and a two-dimensional pattern is formed at the focal plane of the spectrometer. The detector then consists of a two-dimensional surface with sensitive components for detecting the spectral lines.

[0004] Various types of optical semiconductor devices have been used to collect and detect photon signals residing on variously shaped focal planes of analytical spectrometers. Linear and area arrays of light emitting diodes, charge-coupled devices, charge-emitting devices, and plasma-coupled devices have been used to retrieve optical signals from conventional diffraction grating spectrometers as well as echelle grating spectrometers.

One example of a charge coupled device employed to detect a two-dimensional diffraction pattern in an echelle spectrometer is a pixel of 1000 rows × 1000 columns, ie, a total of 1,00,000 pixels.
An XY grid detector of 0,000 pixels is placed at the focal plane to detect spectral lines. The advantage of this arrangement is that almost all signals of the spectrometer, including background noise, can be detected. Disadvantages of this type of detector include inconsistencies between the detected information and the detector array, loss of some spectra, and unnecessarily long read times. A two-dimensional diffraction pattern for continuous wavelength coverage at a given diffraction angle is formed by a wedge stone pattern rather than a rectangle. The use of one or more XY grid detectors causes a shape mismatch between the detector and the diffraction pattern. There is a trade-off between the underfilling / overfilling of the detector and the loss of some diffraction spectra. Furthermore, since all pixels are read in the XY grid, the read time is long, even when most pixels have no useful information.

Another type of solid state detector is described by Bernard in US Pat. No. 4,820,048. In fact, Bernard placed a set of small linear CCD arrays near the background radiation to receive only selected spectral lines, and X
-Remove most pixels in the Y grid. The reading time for detection is shortened by this sharp decrease in the number of pixels,
If the radiation does not fall on the position of the selected line, it cannot be detected at all, and the flexibility of this detector is lower than that of the XY grid.

[0007]

SUMMARY OF THE INVENTION It is, therefore, an object of the present invention to provide a more effective and efficient means for matching a semiconductor solid-state optical device to an analytical spectral signal in the focal plane of an analytical spectrometer. is there.

It is another object of the present invention to provide complete pixel coverage of each echelle diffraction order at that diffraction angle over a non-overlapping spectral range without increasing read time.

It is another object of the present invention to provide a detector having an array of sensitive components positioned exactly along the focal plane of an echelle diffraction spectrometer in the direction of the spectral signal.

Another object of the present invention is as follows. The pixel bays are such that there is a precise tracking between the pixel and the diffraction order, and consequently there is continuous spectral coverage of the entire echelle grating focal plane generated by a specially designed echelle grating spectrometer. Is to provide a solid state detector with a curve.

Another object of the present invention is a detector having curved line pixels, each curved line covering a particular diffraction, and the number of resolution elements available in that order over the non-overlapping spectral range. Is to provide a detector having a curved line of pixels having a selected number of pixels to match.

Another object of the present invention is a detector having curved line pixels, each curved line covering a particular diffraction order and selected to correspond to the length of that order of the non-overlapping spectral range. Is to provide a detector having curved line pixels having a predetermined length.

Another object of the present invention is a detector having pixels of curved lines, each curved line covering a particular diffraction order and corresponding to the size of the resolution element available in that order. The object of the present invention is to provide a detector having curved line pixels having pixels of a selected size.

Another object of the present invention is to provide a detector having an array of pixels along the direction of the diffraction order, the lines of which follow the angle and curvature of the diffraction order as they are. is there.

It is another object of the present invention to provide a detector having pixels arranged along the direction of the diffraction order so that spectral information can be received continuously across the order.

[0016]

The detector according to the present invention comprises:
Consists of a solid state device for use in an Echelle spectrometer. The device has a surface on which the sensitive component is located. The sensitive components or pixels are arranged such that each forms a curved line having a plurality of pixels.
Each curve is mounted on a detector to provide complete spectral coverage of one echelle diffraction order in the spectrometer at that diffraction angle over the non-overlapping spectral range. Each curved line causes the angle and curvature of each diffraction order to follow the angle and curvature as that order changes along the length. This arrangement allows all spectral information along a given diffraction order to be received.

In a preferred embodiment, the detector has a read circuit formed in a solid state device. The read circuit includes a plurality of read circuits each coupled to a portion of a curved line of the pixel, and a plurality of read amplifiers each coupled to the plurality of read circuits.

The detector according to the invention is used with optical components in an echelle spectrometer having an echelle diffraction grating. The echelle grating and the optic cooperate to form a two-dimensional diffraction pattern in the focal plane where the detector is located. The curvature lines of the pixels of the detector are arranged to coincide with the diffraction order in the focal plane. By matching the diffraction order with the pixel line,
All spectral information can be detected along each diffraction order without unduly increasing the reading time.

[0019]

FIG. 1 shows the main components of an echelle spectrometer in which the detector according to the invention is used. Generally, the spectrometer 10 includes an echelle grating 12, a lateral dispersion element 14, such as a prism, and a detector 16. Additional optical elements, such as reflectors 18 and 32, are also included to reflect and focus incident, diffracted and dispersed radiation. Similarly, a mask 20 is used between the dispersive element 14 and the detector 16 to block unwanted radiation to the detector. The shape of the mask 20 corresponds to the shape of a two-dimensional diffraction pattern created at the focal plane of the spectrometer. This pattern shape will be described in detail below.

The electromagnetic field radiation 24 radiated from the source 22 by the slit 26 is first reflected by the reflecting mirror 18, and then becomes an incident wave on the echelle grating 12. Although the diffracted beam 28 has a relatively high order, the incident beam 30 and the diffracted beam 28
The higher order in the diffracted beam is higher because the angle between is smaller than a similar angle in a conventional grating spectrometer. The prism 14 is used to disperse various orders to create a two-dimensional diffraction pattern. The reflector 32 is used to focus a number of spectral lines within a given focal plane of the spectrometer. A detector 16 according to the invention is arranged to block the spectrum at the focal plane. The signal detected by the detector 16 is processed in a reading device 17 described in detail below.

Referring to FIG. 2, a photodetector array 51a,
51n, a CCD array 50 that transfers charge to the corresponding registers 52a, 52b,... 52n, and then to the corresponding read lines 53a, 53b,. Is represented. The data propagating on the lead line is directed to the array control board 55 through the corresponding amplifier and multiplexer. The array control board 55 provides the usual functions necessary for control and operation of the CCD array, such as power and control signals 56, among others. Many lead lines 53a, 53
The nature and function of these controls that direct the way and sequence in which b, ... 53n signals are similar to ordinary prior art. Then the data is organized and the data bus
57a, interface board 59b, and data bus 57b
Through a general digital processor 60.
Digital processor 60 refines control signals 61 coordinated by interface board 59 for transmitting operations performed by array control board 55. Processor 60 also has display functions for displaying the data and processing it as desired data.

Echelle gratings useful in using the detector of the present invention comprise quartz glass from well known manufacturing techniques.
The grating has about 95 grooves per mm cut at a blaze angle of approximately 45 °. In this particular spectrometer, the desired wavelength coverage is about 165 nm to 800 nm,
A diffraction order of 19 to 88 is used.

FIG. 3 shows a two-dimensional diffraction pattern created in the focal plane of the Echelle spectrometer. Depending on the particular spectrometer, each order in the pattern includes multiple resolution elements of various sizes. The size of the resolving element varies with the order of diffraction across the echelle spectrum. Therefore, the size of the resolving element on the order near one end of the pattern is larger than the resolving element in the diffraction order near the other end of the pattern.

As shown in FIG. 3, the diffraction order line 48 in the echelle spectrum is distorted. line
48 are not straight lines and are not strictly parallel to each other. Also, there is no wavelength region for different orders of the same length. However, as is well known, the position, size, spacing, and direction of the lines are predictable for a particular set of parameters of an echelle spectrometer.

FIG. 4 shows the geometric shape of the pixel 52 in the embodiment of the detector according to the present invention. The detector 50 comprises a generally square or rectangular silicon semiconductor chip 54. The plurality of sensitive components or pixels 52 are formed in a silicon chip using well-known semiconductor manufacturing techniques. The sensitive components are arranged to form a plurality of linear arrays 56, each of which describes a curved line on the detector. FIGS. 3 and 4 both show that the curved lines formed on the detector by the pixel array 56 are arranged to coincide with the projection of the echelle diffraction order 48 in the focal plane of the spectrometer. Each curved line of a pixel corresponds to a particular echelle diffraction order projection in the focal plane.

The angle of each curved line of the array 56 is oriented to follow the angle and curvature of the particular diffraction order 48 to be detected by the array. As the angle of the diffraction order 48 changes along the length, the corresponding angle of the pixel array 56 also changes, thereby maintaining a continuous tracking of the diffraction order. This arrangement of the pixel array on the detector makes it possible to follow the diffraction order continuously along the desired overall length. That is, since each pixel array 56 is continuously arranged along the diffraction order projection 48 in the focal plane, each pixel array can continuously receive spectral information across the order over one non-overlapping spectral range.

FIG. 4 shows that the pixel arrays 56 have different lengths. Each array is designed to have a length that matches or approximately equals the length of the diffraction order 48 that is followed by a particular array 56. Since the length of the order of each non-overlapping spectral range changes, so does the length of the pixel array. Also, as the length of the diffraction order increases, the number of resolution elements in the order also increases. In a preferred embodiment of the present invention, the number of pixels 52 in each pixel array 56 corresponds to the number of resolution elements in the diffraction order followed by a particular array. Further, as the size of the resolution element changes from order to order or along an order, the size of each pixel also changes. That is, in the preferred embodiment, the size of each pixel is determined according to the size of the resolution element at which a particular pixel is to be detected. Even in embodiments where the number of pixels in an array is not equal to the number of resolving elements in a particular diffraction order to be detected by the array, the size of the pixels will vary according to the change in the size of the resolving elements in the diffraction order. Can be varied within the array. In other words, irrespective of the benefits realized by matching the number of pixels in the array to the number of resolution elements in the order, a change in the size of the pixels in each array provides certain benefits.
For example, some of their advantages include matching the pixel height to the image height to reduce the overall light sensitive detector to reduce cost while maintaining full coverage. Also, the width of the pixels is optimized to achieve effective reading at the desired resolution.

As described above, for a set of design parameters for an echelle spectrometer, the position, size, spacing and direction of the diffraction order projections in the focal plane are predictable. The preferred embodiment of the detector of the present invention is a method for tracking diffraction orders 19-88 in an echelle spectrometer.
There are nearly 80,000 pixels in 70 arrays. The array is organized as follows.

[0029]

Although not required to make and use the detector of the present invention, a readout circuit can be made using conventional techniques as part of the detector chip. Although no particular shape or arrangement of the read circuit is required, in the preferred embodiment as shown in FIG. 5, the detector has the read circuit incorporated as part of the same semiconductor chip. Each of the 70 pixel arrays is divided into two parts, a left subarray 38 and a right subarray 40. Each of the 140 subarrays has a circuit 42 for reading the subarray pixels. The reading circuit is located between the array of pixels where no spectral information is present and no pixels are located. The amplification circuit 44 is arranged at the end of each sub-array,
It is connected to a plurality of reading circuits. This arrangement allows for variations in integration time, which is useful when more time is needed and does not require unnecessary additional time. As a result, the signal to noise ratio is improved and the read time is reduced. Another description of the reading mechanism has been described above with reference to FIG.

Although the embodiments described above contemplate the use of a silicon substrate for the fabrication of the detector and additional circuitry, in other embodiments, different semiconductor materials may be used. The detector of the present invention can be realized on a monolithic substrate made of one or more different semiconductor materials. For example, the detector is silicon-based and gallium
-Can include arsenic-based regions. For example, such a detector is useful when both the visible and infrared regions are desired. The part of the detector for detecting the visible spectrum is made of silicon, and the part of the detector for detecting the infrared region is gallium-arsenic. Further, the detector can be formed to include three or more materials. For example, the gallium-arsenic region detects the infrared spectrum, the silicon region detects the visible region, and the platinum silicide region detects the ultraviolet region. Each of these embodiments is an application well known to those skilled in the art. All the embodiments described above can realize all the above advantages by using the present invention.

Although the invention has been described with respect to particular embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention as set forth in the appended claims. is there.

[Brief description of the drawings]

FIG. 1 illustrates the main components of an echelle spectrometer in which a detector according to the invention is used.

FIG. 2 is a block diagram of a reading device.

FIG. 3 illustrates a two-dimensional diffraction pattern created in an Echelle spectrometer.

FIG. 4 shows an embodiment of the detector of the present invention, and illustrates a pixel array arranged along a diffraction pattern.

FIG. 5 is a partially enlarged view of FIG. 4, showing how a reading circuit is connected to a pixel array;

[Explanation of symbols]

 12 Echelle grating 14 Lateral dispersion element 16 Detector 18 Reflector 20 Mask 22 Source 24 Electromagnetic radiation 26 Slit 28 Diffracted beam 30 Incident beam 32 Reflector

[Table 1]

[Table 1]

[Table 1]

────────────────────────────────────────────────── ─── Continuation of front page (73) Patent holder 599065901 3120 Hansen Way, Palo Alto, California, U.S.A. S. A. (72) Inventor Lynn Lin Chen 6428, Edgemoor Way, San Jose, California, United States (56) References JP-A-61-56921 (JP, A) JP-A-1-42341 (JP, A) JP-A-5-332835 (JP, A) JP-A-2-2906 (JP, A) US Patent 4,205,229 (US, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01J 3/00 -3/52 G01N 21/00-21/61 G02B 6/00-6/34 G02B 5/18 WPI / L (QUESTEL) Practical file (PATOLIS) Patent file (PATOLIS)

Claims (14)

(57) [Claims] 1. A solid state detector for an echelle spectrometer, comprising: a plurality of sensitive elements arranged on a surface of the detector to form a plurality of sensitive element arrays, wherein the plurality of sensitive element arrays are Forming a corresponding plurality of curved lines on the surface of the detector, each of the curved lines being arranged along a projection of the echelle diffraction order to continuously follow the echelle diffraction order over a non-overlapping spectral range; Where the detector. 2. The detector according to claim 1, wherein each of said curved lines is oriented at an angle corresponding to a projection of a surface of a diffraction order corresponding to said curved lines. . 3. The detector according to claim 1, wherein each of the sensitive element arrays has a length substantially equal to a predetermined wavelength range of a diffraction order to be followed by the sensitive element array over a non-overlapping spectral range. Has a detector. 4. The detector according to claim 3, wherein each sensitive element array has as many sensitive elements as the number of effective resolution elements in the diffraction order to be followed by the sensitive element array. Where the detector. 5. The detector according to claim 4, wherein the size of each sensitive element corresponds to the size of the resolution element to be detected by said sensitive element. 6. The detector according to claim 3, wherein the size of the sensitive element contained in the sensitive element array corresponds to the size of the resolution element available in the diffraction order followed by the sensitive element array. Yes, where the detector. 7. A solid state detector for use in an echelle spectrometer, comprising: a semiconductor chip having a plurality of pixel arrays disposed on a surface thereof, the pixel arrays having a diffraction order at a focal plane in the spectrometer. A semiconductor chip mounted continuously along the projection and providing continuous reception of spectral information across the diffraction order. 8. A spectrometer comprising: an echelle grating for receiving electromagnetic radiation to be analyzed; and a lateral dispersion element for dispersing diffraction orders diffracted from the echelle grating, the echelle grating and the transverse dispersion element. A focal plane comprising a laterally dispersive element wherein the dispersive elements cooperate to form a two-dimensional diffraction pattern at a focal plane of the spectrometer, and a plurality of pixels arranged to form a plurality of curved lines on the detector surface. A detector located at
A spectrometer comprising: a detector in which each curved line is arranged to coincide with a diffraction order at the focal plane; and a circuit connected to the plurality of pixels to generate a signal of spectral information received by the pixel. . 9. The spectrometer of claim 8, wherein each curved line is oriented at an angle corresponding to a projection of the diffraction order on which the curved line is to be matched onto the surface. Spectrometer. 10. The spectrometer of claim 9, wherein each array of pixels has a length substantially equal to a predetermined wavelength range at a focal plane of a diffraction order over which the pixel array is to coincide over a non-overlapping spectral range. Spectrometer that has 11. The spectrometer according to claim 10, wherein each pixel array has the same number of pixels as the number of effective resolution elements in the diffraction order to be matched by the pixel array. Detector. 12. The spectrometer according to claim 11, wherein the size of each pixel corresponds to the size of a resolution element to be detected by the pixel. 13. The spectrometer according to claim 8, further comprising: a mask disposed between the lateral dispersion element and a detector, the mask having a shape corresponding to a two-dimensional diffraction pattern shape. Spectrometer. 14. A solid state detector for an echelle spectrometer having a first plurality of sensitive element arrays made of a first material and forming a corresponding first plurality of curved lines on the detector surface. A first region, wherein the curved lines are arranged along the projection of the echelle diffraction order of the first portion of the non-overlapping spectral range so as to continuously follow the echelle diffraction order over the first portion of the non-overlapping spectral range. A second region having a second plurality of curved lines on the surface of the detector, the second plurality of curved lines being made of a second material, and the second plurality of curved lines being in a non-overlapping spectral range. A second region arranged along the projection of the echelle diffraction order so as to continuously follow the eschal diffraction order over the two portions; and the first and second materials Is selected to optimize the detection of wavelength, so that it is detected in the first and second portions of the spectrum, respectively.